This invention relates to a technique or method of manufacturing lasers of the waveguide type. Such a laser comprises a cavity formed in a block of insulating material such as ceramic. The cavity comprises an elongated slot or channel usually formed along the center line on one of the broad faces of a rectangular block of the insulating material. A flat cover may be bonded to the slotted surface to form the fourth wall of the laser cavity. The flat cover may be of the same insulating material in which the slot is machined, or it may be a metal plate to which one terminal of an RF excitation generator is connected.
One advantage of an RF-excited waveguide gas laser is that the optical gain medium, usually CO.sub.2, is completely isomorphic to the optical mode volume and as a result, all of the optical gain medium fully contributes to the single mode output of the laser. In order to promote the lowest loss waveguide mode, EH.sub.11, of a laser with a cavity of square or rectangular cross section, care must be taken in the fabrication process to ensure that the waveguide has smooth and parallel walls. In the prior art, waveguide laser cavities have been formed by inserting a pair of parallel, spaced shims or spacers between a pair of large ground blocks so that the spacers form the cavity side walls. Any compromise to the parallelism of the waveguide walls will reduce discrimination between the desired lowest order laser oscillatory mode and higher order models, such that unstable oscillation due to transverse mode hopping will result. A slot or channel type waveguide laser, especially one fabricated of hard ceramic material according to the method of the present invention, has important advantages with respect to rigidity, smoothness of waveguide walls, has low susceptibility to misalignment caused by thermal expansion, and can be economically adapted to mass production in either single or multiple slot configurations.